Revealing mistake: Seth is seen holding the alcohol-filled detergent containers, waving his arms and saying to Evan, "You bailed on me!" If the containers were truly full, or even half full, they would be too heavy for him to move up and down so easily. They were obviously empty.

Revealing mistake: When McLovin' is in the car with the police, if you look really closely through the reflection from their glasses, you can see the green screen that is used in movies. When the scene shows the outside of the car, there is nothing around them that would reflect the screen.